<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>缓存全局变量</title>
</head>
<body>
    <input type="button" value="btn" id="btn1">
    <input type="button" value="btn" id="btn2">
    <input type="button" value="btn" id="btn3">
    <input type="button" value="btn" id="btn4">
    <p>1111</p>
    <input type="button" value="btn" id="btn5">
    <input type="button" value="btn" id="btn6">
    <p>2222</p>
    <input type="button" value="btn" id="btn7">
    <input type="button" value="btn" id="btn8">
    <p>3333</p>
    <input type="button" value="btn" id="btn9">
    <input type="button" value="btn" id="btn10">
    <script>
        function getBtn() {
            let oBtn1 = document.getElementById('btn1')
            let oBtn3 = document.getElementById('btn3')
            let oBtn5 = document.getElementById('btn5')
            let oBtn7 = document.getElementById('btn7')
            let oBtn9 = document.getElementById('btn9')
        }

        function getBtn2() {
            let obj = document
            let oBtn1 = obj.getElementById('btn1')
            let oBtn3 = obj.getElementById('btn3')
            let oBtn5 = obj.getElementById('btn5')
            let oBtn7 = obj.getElementById('btn7')
            let oBtn9 = obj.getElementById('btn9')
        }
    </script>
</body>
</html>